This invention relates generally to a vehicle occupant restraint system and more particularly to a tension eliminating mechanism for a belt retractor.
Occupant restraint systems for motor vehicles commonly employ a shoulder belt which extends over the shoulder and across the chest of the seated occupant. Shoulder belts are found in so called three point belt systems which utilize a single length of belt and in two belt systems which has a shoulder bit and a separate lap belt. In both systems the shoulder belt is arranged to be anchored by a buckle mounted inboard of the occupant seating position and anchored at the other end to the vehicle by means of a belt retractor. The belt retractor utilized in such systems commonly utilizes a relatively strong windup spring which rotates a spool to wind a substantial portion of the shoulder belt onto the spool.
Utilization of a relatively strong windup spring in the retractor results in a level of shoulder belt load across the chest which is annoying to some seat occupants, so much so that some occupants may even elect not to utilize the seat belt system. Consequently, it is desirable to provide some means for eliminating the tension of the windup spring on the belt so as to reduce or eliminate the tension of the shoulder belt across the chest of the occupant.
It is known to provide a belt retractor with a winding prevention mechanism for the purpose of reducing or eliminating the tension of the shoulder belt across the chest of the occupant, and such systems are shown in U.S. Pat. No. 4,065,072 issued in the name of Joseph J. Magyar on Dec. 27, 1977, U.S. Pat. No. 3,973,786 issued in the name of Lloyd W. Rogers, Jr., on August 1976 and U.S. Pat. No. 3,869,098 issued in the name of Raymond G. Sprecher on Mar. 4, 1975. However, one of the disadvantages of the prior known tension eliminating mechanisms is that they are relatively costly.